Myo-Inositol appears to be universally distributed in nature and scyllo-inositol is found to accompany myo- whenever sufficiently sensitive methods have been used. While myo-inositol has a clearly defined function as a precursor of the phosphoinositides, it is widely held that it has other important functions also. Scyllo-Inositol has no known function. These two inositols are found in high concentration in nervous tissue. The objectives of the proposed research are to determine the sources of scyllo-inos tol in mammals, and its distribution, especially relative to myo-inositol at the cellular level. To this end we are studying the enzymes which reduce myo-inosose-2 to myo- and scyllo-inositol in mammals and employing mass fragmentography (multiple ion detection, MID) to measure myo-inositol in 5-50 ng dry weight brain tissue slices. We hope to begin the measurement of scyllo-inositol in the larger of these tissues in the next year. We are using the MID method for measuring myo-inositol to determine its distribution at the cellular level (large single cells in the CNS, to small populations of cells). We are also studying the affinity chromatography of L-myo-inositol-1-P synthase in order to sufficiently purify it to enable us to prepare fluorescent antibody so as to attempt the localization of this in tissues, especially the CNS. BIBLIOGRAPHIC REFERENCES: Hipps, P.P., Eveland, M.R., Laird, M.H. and Sherman, W.R.: The identification of myo-inositol:NAD(P) plus oxidoreductase in mammalian brain, Biochem. Biophys. Res. Commun. 68:1133, 1976. Allison, J.H., Blisner, M.E., Holland, W.H., Hipps, P.P., and Sherman, W.R.: Increased brain myo-inositol 1-phosphate in lithium-treated rats, Biochem. Biophys. Res. Commun. 71:664, 1976.